This invention relates to a tool for driving metal fasteners, such as nails, brads, tacks, staples, and the like in a frame and setting its rear closing panel.
It is well-known that for most frames the glass and the decorative motif or subject to be displayed are applied to the front moulding of the frame by means of a closing panel which is fixed at the back of the frame.
The fixing is usually made by driving the metal fastener in the internal side of the frame in a substantially parallel direction to the frame's plane, so that the projecting parts of the driven fastener make up a suitable means to prevent the detaching of the panel from the frame.
The metal fasteners have always been applied manually and this has obviously taken long working times and has involved high costs to get a finished frame.
In order to overcome these inconveniences the common stapling-machines have been used namely those mechanically worked machines for driving staples in which, by preloading means, a driver causes the staples to be ejected, that is those fixing components consisting of a thin U-shaped section.
The use of these machines turned out to be extremely difficult since they must be used in a position which is completely different from that one for which they are made. In fact, they are suitable for driving the staple according to a direction which is perpendicular to the plane on which they are put, while, in the specific case of the frame, the driving must be effected according to a direction which is parallel to the plane on which the machine is placed. The working of its driving means turns out to be extremely difficult when placing the tool in such a way that the driving of staples is made according to this last direction.
Further inconveniences of these machines consist in the fact that they do not allow a proper driving of the staple which, for fixing the panel, must be inserted into the frame so that its bridging part exerts a pressure on the panel. This is not possible with the above mentioned machines since the staple becomes disconnected from the support plane and consequently it does not adhere to the panel to be fixed.
Machines which are suitable for driving the fixing members of the panel in the frame have also been created; said members consist of substantially rhomboidal plates which are inserted by their top into the frame, their remaining portion being the fixing member of the panel.
But these machines still pose some problems concerning both the application of the fixing members and the safety of the fixing itself.
A first problem is due to the fact that the rhomboidal fixing member being inserted by its top in the frame may easily get out from it owing to its shape deflecting outward the frame section.
A further problem lies in the fact that the rhomboidal fixing plate must be thin both for having a less penetrating section in the frame and not to cause its breakage and in order to demand from the driver of the driving machine as little force as possible. In this situation, the rhomboidal fixing member is easily capable of being deformed, it is subject to distortions or breakages and, for large-sized frames, it does not ensure the necessary fixing capability.
Another drawback of these machines is due to the fact that the end of the driver joined together with the rhomboidal plate in order to cause it to be ejected and driven must be forcedly shaped in a complementary way for guiding the plate along a special ejection passage of the machine. It is clear that undesired shiftings to the rhomboidal plate in respect of the optimum position where it receives the end of the driver may occur and this can cause, owing to the displacements of the plate, the machine to be jammed.
Moreover, the driver of the machine will suit only for rhomboidal plates of particular size, beyond which it will be no more suitable.